scholarly journals Event Studies of High‐Latitude FACs With Inverse and Assimilative Analysis of AMPERE Magnetometer Data

2020 ◽  
Vol 125 (3) ◽  
Author(s):  
Yining Shi ◽  
Delores J. Knipp ◽  
Tomoko Matsuo ◽  
Liam Kilcommons ◽  
Brian Anderson
Keyword(s):  
High Latitude ◽  
Event Studies ◽  
Magnetometer Data

scholarly journals Comparison of the magnetic equivalent convection direction and ionospheric convection observed by the SuperDARN radars

2006 ◽  
Vol 24 (11) ◽  
pp. 2981-2990 ◽  
Author(s):  
L. V. Benkevitch ◽  
A. V. Koustov ◽  
J. Liang ◽  
J. F. Watermann
Keyword(s):  
Local Time ◽  
High Latitude ◽  
Early Morning ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Ionospheric Convection ◽  
Morning Sector ◽  
Magnetometer Data ◽  
Different Seasons

Abstract. SuperDARN radar and high-latitude magnetometer observations are used to statistically investigate quality of the convection direction estimates from magnetometer data if assumption is made that the magnetic equivalent convection vector (MEC) corresponds to the convection direction. The statistics includes five full days, ~75 000 of joint individual measurements for different seasons. It is demonstrated that the best (worst) agreement between the MEC and ionospheric convection occurs for the sunlit, summer (dark, winter) ionosphere. Overall, the MEC direction is reasonable (deviates less than 45° from the SuperDARN direction) in at least ~55% of points and it is better for the latitudes of the auroral oval. In terms of the magnetic local time, the agreement is the best (worst) in the dusk (early morning) sector. Possible reasons for differences between the MEC and ionospheric convection directions are discussed.

scholarly journals High-latitude poynting flux from combined Iridium and SuperDARN data

2004 ◽  
Vol 22 (8) ◽  
pp. 2861-2875 ◽  
Author(s):  
C. L. Waters ◽  
B. J. Anderson ◽  
R. A. Greenwald ◽  
R. J. Barnes ◽  
J. M. Ruohoniemi
Keyword(s):  
Electric Fields ◽  
Energy Flux ◽  
High Latitude ◽  
Electromagnetic Energy ◽  
Total Power ◽  
Data Sets ◽  
Poynting Flux ◽  
Magnetic Perturbations ◽  
Magnetometer Data ◽  
A New Technique

Abstract. Field-aligned currents convey stress between the magnetosphere and ionosphere, and the associated low altitude magnetic and electric fields reflect the flow of electromagnetic energy to the polar ionosphere. We introduce a new technique to measure the global distribution of high latitude Poynting flux, S||, by combining electric field estimates from the Super Dual Auroral Radar Network (SuperDARN) with magnetic perturbations derived using magnetometer data from the Iridium satellite constellation. Spherical harmonic methods are used to merge the data sets and calculate S|| for any magnetic local time (MLT) from the pole to 60° magnetic latitude (MLAT). The effective spatial resolutions are 2° MLAT, 2h MLT, and the time resolution is about one hour due to the telemetry rate of the Iridium magnetometer data. The technique allows for the assessment of high-latitude net S|| and its spatial distribution on one hour time scales with two key advantages: (1) it yields the net S|| including the contribution of neutral winds; and (2) the results are obtained without recourse to estimates of ionosphere conductivity. We present two examples, 23 November 1999, 14:00-15:00 UT, and 11 March 2000, 16:00-17:00 UT, to test the accuracy of the technique and to illustrate the distributions of S|| that it gives. Comparisons with in-situ S|| estimates from DMSP satellites show agreement to a few mW/m2 and in the locations of S|| enhancements to within the technique's resolution. The total electromagnetic energy flux was 50GW for these events. At auroral latitudes, S|| tends to maximize in the morning and afternoon in regions less than 5° in MLAT by two hours in MLT having S||=10 to 20mW/m2 and total power up to 10GW. The power poleward of the Region 1 currents is about one-third of the total power, indicating significant energy flux over the polar cap.

scholarly journals A survey of magnetopause FTEs and associated flow bursts in the polar ionosphere

2000 ◽  
Vol 18 (4) ◽  
pp. 416-435 ◽  
Author(s):  
D. A. Neudegg ◽  
S. W. H. Cowley ◽  
S. E. Milan ◽  
T. K. Yeoman ◽  
M. Lester ◽  
...  
Keyword(s):  
Solar Wind ◽  
Case Studies ◽  
High Latitude ◽  
Geomagnetic Field ◽  
Magnetospheric Physics ◽  
Polar Ionosphere ◽  
Convection Pattern ◽  
Transfer Event ◽  
Extensive Survey ◽  
Magnetometer Data

Abstract. Using the Equator-S spacecraft and SuperDARN HF radars an extensive survey of bursty reconnection at the magnetopause and associated flows in the polar ionosphere has been conducted. Flux transfer event (FTE) signatures were identified in the Equator-S magnetometer data during periods of magnetopause contact in January and February 1998. Assuming the effects of the FTEs propagate to the polar ionosphere as geomagnetic field-aligned-currents and associated Alfvén-waves, appropriate field mappings to the fields-of-view of SuperDARN radars were performed. The radars observed discrete ionospheric flow channel events (FCEs) of the type previously assumed to be related to pulse reconnection. Such FCEs were associated with \\sim80% of the FTEs and the two signatures are shown to be statistically associated with greater than 99% confidence. Exemplary case studies highlight the nature of the ionospheric flows and their relation to the high latitude convection pattern, the association methodology, and the problems caused by instrument limitations.Key words: Ionosphere (polar ionosphere) · Magnetospheric physics (magnetosphere-ionosphere interaction; solar wind-magnetosphere interactions)

scholarly journals Statistical survey of day-side magnetospheric current flow using Cluster observations: magnetopause

2017 ◽  
Vol 35 (3) ◽  
pp. 645-657 ◽  
Author(s):  
Evelyn Liebert ◽  
Christian Nabert ◽  
Christopher Perschke ◽  
Karl-Heinz Fornaçon ◽  
Karl-Heinz Glassmeier
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Current Flow ◽  
Fluxgate Magnetometer ◽  
Current Direction ◽  
Plasma Properties ◽  
Close Vicinity ◽  
Magnetometer Data ◽  
Current Densities ◽  
Statistical Survey

Abstract. We present a statistical survey of current structures observed by the Cluster spacecraft at high-latitude day-side magnetopause encounters in the close vicinity of the polar cusps. Making use of the curlometer technique and the fluxgate magnetometer data, we calculate the 3-D current densities and investigate the magnetopause current direction, location, and magnitude during varying solar wind conditions. We find that the orientation of the day-side current structures is in accordance with existing magnetopause current models. Based on the ambient plasma properties, we distinguish five different transition regions at the magnetopause surface and observe distinctive current properties for each region. Additionally, we find that the location of currents varies with respect to the onset of the changes in the plasma environment during magnetopause crossings.

scholarly journals The effects of an interplanetary shock on the high-latitude ionospheric convection during an IMF <I>B<sub>y</sub></I>-dominated period

2008 ◽  
Vol 26 (9) ◽  
pp. 2937-2951 ◽  
Author(s):  
I. Coco ◽  
E. Amata ◽  
M. F. Marcucci ◽  
D. Ambrosino ◽  
J.-P. Villain ◽  
...  
Keyword(s):  
High Latitude ◽  
Geomagnetic Field ◽  
Dynamic Pressure ◽  
Interplanetary Shock ◽  
Ionospheric Convection ◽  
Vortical Structures ◽  
Magnetometer Data ◽  
Northern High Latitude ◽  
Lobe Reconnection ◽  
Very High

Abstract. On 6 January 1998 an interplanetary shock hit the magnetosphere around 14:15 UT and caused a reconfiguration of the northern high-latitude ionospheric convection. We use SuperDARN, spacecraft and ground magnetometer data to study such reconfiguration. We find that the shock front was tilted towards the morning flank of the magnetosphere, while the Interplanetary Magnetic Field (IMF) was By-dominated, with By<0, IMF Bz>0 and |By|>>Bz. As expected, the magnetospheric compression started at the first impact point of the shock on the magnetopause causing an increase of the Chapman-Ferraro current from dawn to dusk and yielding an increase of the geomagnetic field at the geostationary orbit and on the ground. Moreover, the high-latitude magnetometer data show vortical structures clearly related to the interaction of the shock with the magnetosphere-ionosphere system. In this context, the SuperDARN convection maps show that at very high latitudes above the northern Cusp and in the morning sector, intense sunward convection fluxes appear, well correlated in time with the SI arrival, having a signature typical for Bz>0 dominated lobe reconnection. We suggest that in this case the dynamic pressure increase associated to the shock plays a role in favouring the setting up of a new lobe merging line albeit |By|>>Bz≥0.

Inverse procedure for high‐latitude ionospheric electrodynamics: Analysis of satellite‐borne magnetometer data

2015 ◽  
Vol 120 (6) ◽  
pp. 5241-5251 ◽  
Author(s):  
Tomoko Matsuo ◽  
Delores J. Knipp ◽  
Arthur D. Richmond ◽  
Liam Kilcommons ◽  
Brian J. Anderson
Keyword(s):  
High Latitude ◽  
Ionospheric Electrodynamics ◽  
Magnetometer Data ◽  
Inverse Procedure

scholarly journals High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes

1997 ◽  
Vol 15 (12) ◽  
pp. 1548-1556 ◽  
Author(s):  
D. M. Wright ◽  
T. K. Yeoman ◽  
P. J. Chapman
Keyword(s):  
Field Line ◽  
High Latitude ◽  
Vertical Component ◽  
Low Frequency ◽  
Mhd Waves ◽  
Ulf Waves ◽  
Large Spatial Scale ◽  
Field Line Resonances ◽  
Doppler Data ◽  
Magnetometer Data

Abstract. A quantitative study of observations of the ionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a high-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has been undertaken. The signatures, which are clearly correlated with pulsations in ground magnetometer data, exhibit periods in the range 100–400 s and have azimuthal wave numbers in the range 3–8. They are interpreted here as local field line resonances. Phase information provided by O- and X-mode Doppler data support the view that these are associated with field line resonances having large azimuthal scale sizes. The relative phases and amplitudes of the signatures in the Doppler and ground magnetometer data are compared with a model for the generation of Doppler signatures from incident ULF waves. The outcome suggests that the dominant mechanism involved in producing the Doppler signature is the vertical component of an E × B bulk motion of the local plasma caused by the electric field perturbation of the ULF wave.Key words. Auroral ionosphere · Magnetosphere-ionosphere interactions · MHD waves and instabilities HF Doppler · ULF Waves

Sign in / Sign up

Export Citation Format

Share Document